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3

Heat Of Compression Air Dryer

air dryer hoc

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#1 ponnusj

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Posted 26 October 2023 - 03:10 AM

Hi,

I am studying the energy savings of installing a Heat of Compression (HOC) dryer in an Instrument Air (IA) circuit.

 

Kindly share your experiences in design and operation of a HOC dryer in IA circuit.

 

Thanks



#2 breizh

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Posted 26 October 2023 - 05:50 AM

Hi,

Consider this brochure from reputable vendor .

Breizh



#3 ponnusj

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Posted 26 October 2023 - 06:47 AM

Thanks breizh, for the brochure.

 

I am a bit sceptical about the claims of energy consumption reduction by 75%.

I agree that the electricity requirement of the blower and heater are eliminated from a Blower Purge type dryer.

But as the compressed air (CA) stream used for regeneration (heating and cooling) has to pass though an additional dryer bed wouldn't the compressor have to operate at a higher pressure (+0.5 bar) which will increase the compressor electricity consumption?

Am I missing something?

 

Hence seeking experience of design and operation of HOC dryers.

 

 



#4 Pilesar

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Posted 26 October 2023 - 10:35 AM

I have no experience with HOC dryers. The brochure shows a great design. Pressure drop for the regen stream will be much lower than 0.5 bar since the regen flow is only part of the total air stream. The extra energy is not free, but should be very low.



#5 breizh

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Posted 26 October 2023 - 07:28 PM

Hi,

If you want meaningful answer, write down a specification sheet and submit it to vendors, ask for a budget price and operating cost breakdown.

Atlas Copco and Ingersoll Rand should be the companies to begin with, you may have other references in mind.

Note: Atlas Copco is reviewing different technologies with pros and cons.

 

Good luck. 

Breizh 



#6 Art Montemayor

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Posted 26 October 2023 - 11:53 PM

Ponnusj:

 

I’ve designed, built, and operated adsorption dryers for air, CO2, Oxygen, Nitrous Oxide, and other gases to meet conditions of moisture content down to 1 ppm volume.  What you are describing is nothing more than an adsorption dryer for compressed air that relies on the discharge temperature of the associated air compressor discharge temperature as the source of heat for regenerating the spent adsorber bed.

 

I agree with your suspicions that you can’t expect to save 75% of regeneration heat requirements with the proposed system design.  In order to fully analyze the operation and calculate any energy consumption you have to first state the basic design, such as the very poor moisture removal, the need for more valves, the bigger adsorbent beds, and the required drop in pressure from the compressor discharge.

 

The pressure drop is a basic requirement in the flow diagram furnished by Breizh.  This is not a result of the adsorbent bed solely.  The basic pressure drop is a requirement in order to divert the hot compressor flow through regeneration and cooling and subsequently enter the drying adsorbent bed.  The IR flow diagram doesn’t show this detail very well, so that need is not perceived.

 

Basically this system is adequate if you only need -40 F dew point – which isn’t very dry.  And IR doesn’t tell us what compressor discharge temperature is required in order to achieve that dew point.  The normal discharge temperature I would expect is approx. 225 F – which is not very hot considering it has to vaporize the captured water in the spent bed.  A higher discharge temperature would mean a larger required compression ratio – which would mean more hp and more oil decomposition and adsorbent bed contamination.  These factors would be trade-offs and might be acceptable.  It all depends on what one needs, can afford, or tolerate.  There are no free rides or free lunches in life.


Edited by Art Montemayor, 02 November 2023 - 01:24 PM.
typos


#7 ponnusj

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Posted 31 October 2023 - 02:48 AM

Art,

You have articulated my thoughts clearly in your response, thanks.

 

I have designed and operated IA dryers for industrial facilities using heatless purge and heated blower type dryers.

I am currently into industrial energy efficiency/conservation and when I came across HOC dryers with fancy claims was a bit puzzled why the industry is not adopting them.

 

That is the reason I was sourcing for first hand experience in designing or operating HOC facilities.






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